Common search space for machine type communications

ABSTRACT

Certain aspects of the present disclosure generally relate to wireless communications and more specifically to search space configuration in systems utilizing devices with limited communications resources, such as machine type communication (MTC) devices and enhanced MTC (eMTC) devices. An example method generally includes receiving a physical random access channel (PRACH) signal from a first user equipment (UE) on a first narrowband region within a wider system bandwidth and transmitting, in response to the PRACH signal, a random access response (RAR) signal in a first search space in a second narrowband region in at least a first subframe.

CLAIM OF PRIORITY UNDER 35 U.S.C. § 119

The present Application for Patent is a continuation of U.S. patentapplication Ser. No. 15/174,678, filed Jun. 6, 2016, which claimspriority to U.S. Provisional Application No. 62/191,253, filed Jul. 10,2015, and U.S. Provisional Application No. 62/288,425, filed Jan. 28,2016, all of which are assigned to the assignee of the presentapplication and hereby expressly incorporated by reference herein intheir entireties.

BACKGROUND Field of the Invention

Certain aspects of the present disclosure generally relate to wirelesscommunications and more specifically to search space configuration insystems utilizing devices with limited communications resources, such asmachine type communication(s) (MTC) devices and enhanced or evolved MTC(eMTC) devices.

Description of Related Art

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple-access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) including LTE-Advanced systemsand orthogonal frequency division multiple access (OFDMA) systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-input single-output, multiple-inputsingle-output or a multiple-input multiple-output (MIMO) system.

A wireless communication network may include a number of base stationsthat can support communication for a number of wireless devices.Wireless devices may include user equipments (UEs). Some UEs may beconsidered machine type communication (MTC) UEs, which may includeremote devices, that may communicate with a base station, another remotedevice, or some other entity. Machine type communications (MTC) mayrefer to communication involving at least one remote device on at leastone end of the communication and may include forms of data communicationwhich involve one or more entities that do not necessarily need humaninteraction. MTC UEs may include UEs that are capable of MTCcommunications with MTC servers and/or other MTC devices through PublicLand Mobile Networks (PLMN), for example.

SUMMARY

The systems, methods, and devices of the disclosure each have severalaspects, no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this disclosure as expressedby the claims which follow, some features will now be discussed briefly.After considering this discussion, and particularly after reading thesection entitled “Detailed Description” one will understand how thefeatures of this disclosure provide advantages that include improvedcommunications between access points and stations in a wireless network.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a base station (BS). The method generally includesreceiving a physical random access channel (PRACH) signal from a firstuser equipment (UE) on a first narrowband region within a wider systembandwidth and transmitting, in response to the PRACH signal, a randomaccess response (RAR) signal in a first search space in a secondnarrowband region in at least a first subframe.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a user equipment (UE). The method generally includestransmitting a physical random access channel (PRACH) signal to a basestation (BS) on a first narrowband region within a wider systembandwidth and receiving, in response to the PRACH signal, a randomaccess response (RAR) signal in a first search space in a secondnarrowband region in at least a first subframe.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a base station (BS). The method generally includesdetermining a coverage enhancement (CE) level of a UE, initializing ascrambling sequence for transmitting a signal to the UE based on the CElevel, scrambling the signal to the UE with the scrambling sequence, andtransmitting the scrambled signal to the UE.

Certain aspects of the present disclosure provide a method for wirelesscommunications by a user equipment (UE). The method generally includesinitializing a scrambling sequence based on a coverage enhancement (CE)level of the UE, receiving a signal scrambled with the scramblingsequence, and descrambling the signal with the scrambling sequence.

Certain aspects of the present disclosure provide a method for wirelesscommunications performed by a base station (BS). The method generallyincludes scrambling a first demodulation reference signal (DM-RS) to afirst UE with a first scrambling sequence initialized with a scramblingsequence initialization, scrambling a second DM-RS to a second UE with asecond scrambling sequence initialized with the scrambling sequenceinitialization, and transmitting the scrambled first DM-RS to the firstUE and the scrambled second DM-RS to the second UE in a same searchspace.

Certain aspects of the present disclosure provide a method for wirelesscommunications performed by a user equipment (UE). The method generallyincludes receiving a first demodulation reference signal (DM-RS)scrambled with a first scrambling sequence initialized with a scramblingsequence initialization, receiving a signal scrambled with the firstscrambling sequence in a search space, wherein at least a second DM-RSscrambled with a second scrambling sequence initialized with thescrambling sequence initialization is transmitted in the search space,and descrambling the signal with the first scrambling sequence.

Certain aspects of the present disclosure provide a method for wirelesscommunications performed by a base station (BS). The method generallyincludes determining a set of repetitions for transmitting a downlinkchannel, determining a power boost value for the downlink channel,transmitting an indication of the power boost value for the downlinkchannel, and transmitting the downlink channel based on the set ofrepetitions and the power boost value.

Certain aspects of the present disclosure provide a method for wirelesscommunications performed by a user equipment (UE). The method generallyincludes determining a first set of repetitions for receiving a downlinkchannel, determining a received signal quality, determining a second setof repetitions for receiving the downlink channel based at least in parton the first set of repetitions and the received signal quality, andreceiving the downlink channel based on the second set of repetitions.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes at least oneprocessor configured to receive a physical random access channel (PRACH)signal from a first user equipment (UE) on a first narrowband regionwithin a wider system bandwidth and transmit, in response to the PRACHsignal, a random access response (RAR) message in a first search spacein a second narrowband region in at least a first subframe.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes at least oneprocessor configured to scramble a first demodulation reference signal(DM-RS) to a first UE with a first scrambling sequence initialized witha scrambling sequence initialization, scramble a second DM-RS to asecond UE with a second scrambling sequence initialized with thescrambling sequence initialization, and transmit the scrambled firstDM-RS to the first UE and the scrambled second DM-RS to the second UE ina same search space.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes at least oneprocessor configured to transmit a physical random access channel(PRACH) signal to a base station (BS) on a first narrowband regionwithin a wider system bandwidth and receive, in response to the PRACHsignal, a random access response (RAR) message in a first search spacein a second narrowband region in at least a first subframe.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes at least oneprocessor configured to receive a first demodulation reference signal(DM-RS) scrambled with a first scrambling sequence initialized with ascrambling sequence initialization, receive a signal scrambled with thefirst scrambling sequence in a search space, wherein at least a secondDM-RS scrambled with a second scrambling sequence initialized with thescrambling sequence initialization is transmitted in the search space,and descramble the signal with the first scrambling sequence.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means forreceiving a physical random access channel (PRACH) signal from a firstuser equipment (UE) on a first narrowband region within a wider systembandwidth and means for transmitting, in response to the PRACH signal, arandom access response (RAR) message in a first search space in a secondnarrowband region in at least a first subframe.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means forscrambling a first demodulation reference signal (DM-RS) to a first UEwith a first scrambling sequence initialized with a scrambling sequenceinitialization, means for scrambling a second DM-RS to a second UE witha second scrambling sequence initialized with the scrambling sequenceinitialization, and means for transmitting the scrambled first DM-RS tothe first UE and the scrambled second DM-RS to the second UE in a samesearch space.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means fortransmitting a physical random access channel (PRACH) signal to a basestation (BS) on a first narrowband region within a wider systembandwidth and means for receiving, in response to the PRACH signal, arandom access response (RAR) message in a first search space in a secondnarrowband region in at least a first subframe.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means forreceiving a first demodulation reference signal (DM-RS) scrambled with afirst scrambling sequence initialized with a scrambling sequenceinitialization, means for receiving a signal scrambled with the firstscrambling sequence in a search space, wherein at least a second DM-RSscrambled with a second scrambling sequence initialized with thescrambling sequence initialization is transmitted in the search space,and means for descrambling the signal with the first scramblingsequence.

Certain aspects of the present disclosure provide a computer readablemedium for wireless communications. The computer readable mediumgenerally includes code for receiving a physical random access channel(PRACH) signal from a first user equipment (UE) on a first narrowbandregion within a wider system bandwidth and code for transmitting, inresponse to the PRACH signal, a random access response (RAR) message ina first search space in a second narrowband region in at least a firstsubframe.

Certain aspects of the present disclosure provide a computer readablemedium for wireless communications. The computer readable mediumgenerally includes code for scrambling a first demodulation referencesignal (DM-RS) to a first UE with a first scrambling sequenceinitialized with a scrambling sequence initialization, code forscrambling a second DM-RS to a second UE with a second scramblingsequence initialized with the scrambling sequence initialization, andcode for transmitting the scrambled first DM-RS to the first UE and thescrambled second DM-RS to the second UE in a same search space.

Certain aspects of the present disclosure provide a computer readablemedium for wireless communications. The computer readable mediumgenerally includes code for transmitting a physical random accesschannel (PRACH) signal to a base station (BS) on a first narrowbandregion within a wider system bandwidth and code for receiving, inresponse to the PRACH signal, a random access response (RAR) message ina first search space in a second narrowband region in at least a firstsubframe.

Certain aspects of the present disclosure provide a computer readablemedium for wireless communications. The computer readable mediumgenerally includes code for receiving a first demodulation referencesignal (DM-RS) scrambled with a first scrambling sequence initializedwith a scrambling sequence initialization, code for receiving a signalscrambled with the first scrambling sequence in a search space, whereinat least a second DM-RS scrambled with a second scrambling sequenceinitialized with the scrambling sequence initialization is transmittedin the search space, and code for descrambling the signal with the firstscrambling sequence.

Numerous other aspects are provided including methods, apparatus,systems, computer program products, computer readable medium, andprocessing systems.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 is a block diagram conceptually illustrating an example wirelesscommunication network, in accordance with certain aspects of the presentdisclosure.

FIG. 2 is a block diagram conceptually illustrating an example of anevolved nodeB (eNB) in communication with a user equipment (UE) in awireless communications network, in accordance with certain aspects ofthe present disclosure.

FIG. 3 is a block diagram conceptually illustrating an example framestructure for a particular radio access technology (RAT) for use in awireless communications network, in accordance with certain aspects ofthe present disclosure.

FIG. 4 illustrates example subframe formats for the downlink with anormal cyclic prefix, in accordance with certain aspects of the presentdisclosure.

FIGS. 5A and 5B illustrate an example of MTC co-existence within awideband system, such as LTE, in accordance with certain aspects of thepresent disclosure.

FIG. 6 illustrates an exemplary mapping of DL narrowband regions to ULnarrowband regions, in accordance with certain aspects of the presentdisclosure.

FIG. 7 illustrates an exemplary operation for wireless communicationsthat may be performed by a BS, in accordance with certain aspects of thepresent disclosure.

FIG. 8 illustrates an exemplary operation for wireless communicationsthat may be performed by a UE, in accordance with certain aspects of thepresent disclosure.

FIG. 9 illustrates exemplary techniques for multiplexing MPDCCHs, inaccordance with certain aspects of the present disclosure.

FIG. 10 illustrates exemplary MPDCCH common search spaces, in accordancewith certain aspects of the present disclosure.

FIG. 11 illustrates an exemplary operation for wireless communicationsthat may be performed by a BS, in accordance with certain aspects of thepresent disclosure.

FIG. 12 illustrates an exemplary operation for wireless communicationsthat may be performed by a UE, in accordance with certain aspects of thepresent disclosure.

FIG. 13 illustrates an exemplary operation for wireless communicationsthat may be performed by a BS, in accordance with certain aspects of thepresent disclosure.

FIG. 14 illustrates an exemplary operation for wireless communicationsthat may be performed by a UE, in accordance with certain aspects of thepresent disclosure.

FIG. 15 illustrates an exemplary transmission timelines of a BS and a UEoperating according to aspects of the present disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure provide techniques and apparatus forenhanced paging messages and random access response (RAR) messages fordevices with limited communication resources, such as low cost (LC)machine type communication (MTC) devices, LC enhanced MTC (eMTC)devices, etc. MTC and eMTC devices may receive MTC physical downlinkcontrol channel (MPDCCH) transmissions carrying paging messages and RARmessages. MTC and eMTC devices may attempt to decode MPDCCH candidatesin search spaces of time and frequency transmission resources. MPDCCHsmay be transmitted in common search spaces (CSS). Base stations maytransmit MPDCCHs conveying paging and RAR messages in CSS selected basedat least in part on a coverage enhancement (CE) level of a receiving UEand/or a subband used by a UE when transmitting a physical random accesschannel (PRACH). To enhance coverage of certain devices, such as MTC andeMTC devices, “bundling” may be utilized in which certain transmissionsare sent as a bundle of transmissions, for example, with the sameinformation transmitted over multiple subframes.

Accordingly, as will be described in more detail below, the techniquespresented herein may allow for cells to transmit and MTC devices toreceive paging and RAR messages that are bundled to achieve CE of up to15 dB. In addition, techniques presented herein may allow for cells totransmit and MTC devices to receive paging and RAR messages insituations when a cell needs to transmit both paging and RAR messages inone subframe, sometimes referred to as a collision between paging andRAR messages.

The techniques described herein may be used for various wirelesscommunication networks such as Code Division Multiple Access (CDMA)networks, Time Division Multiple Access (TDMA) networks, FrequencyDivision Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“network” and “system” are often used interchangeably. A CDMA networkmay implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA), TimeDivision Synchronous CDMA (TD-SCDMA), and other variants of CDMA.cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network mayimplement a radio technology such as Global System for MobileCommunications (GSM). An OFDMA network may implement a radio technologysuch as Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc. UTRA andE-UTRA are part of Universal Mobile Telecommunication System (UMTS).3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A), in bothfrequency division duplex (FDD) and time division duplex (TDD), are newreleases of UMTS that use E-UTRA, which employs OFDMA on the downlinkand SC-FDMA on the uplink. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM aredescribed in documents from an organization named “3rd GenerationPartnership Project” (3GPP). cdma2000 and UMB are described in documentsfrom an organization named “3rd Generation Partnership Project 2”(3GPP2). The techniques described herein may be used for the wirelessnetworks and radio technologies mentioned above as well as otherwireless networks and radio technologies. For clarity, certain aspectsof the techniques are described below for LTE/LTE-A, and LTE/LTE-Aterminology is used in much of the description below. LTE and LTE-A arereferred to generally as LTE.

FIG. 1 illustrates an example wireless communication network 100 withbase stations (BSs) and user equipments (UEs), in which aspects of thepresent disclosure may be practiced.

For example, one or more paging procedure enhancements for certain UEs(e.g., LC MTC UEs, LC eMTC UEs, etc.) in the wireless communicationnetwork 100 may be supported. According to the techniques presentedherein, the BSs and LC UE(s) in the wireless communication network 100may be able to determine, from the available system bandwidth supportedby the wireless communication network 100, which narrowband region(s)the LC UE(s) should monitor for a bundled paging message transmittedfrom the BSs in the wireless communication network 100. Also, accordingto techniques presented herein, the BSs and/or LC UE(s) in the wirelesscommunication network 100 may be able to determine and/or adapt thebundling size for the paging message based on one or more triggers inthe wireless communication network 100.

The wireless communication network 100 may be an LTE network or someother wireless network. Wireless communication network 100 may include anumber of evolved NodeBs (eNBs) 110 and other network entities. An eNBis an entity that communicates with user equipments (UEs) and may alsobe referred to as a base station, a Node B, an access point (AP), etc.Each eNB may provide communication coverage for a particular geographicarea. In 3GPP, the term “cell” can refer to a coverage area of an eNBand/or an eNB subsystem serving this coverage area, depending on thecontext in which the term is used.

An eNB may provide communication coverage for a macro cell, a pico cell,a femto cell, and/or other types of cell. A macro cell may cover arelatively large geographic area (e.g., several kilometers in radius)and may allow unrestricted access by UEs with service subscription. Apico cell may cover a relatively small geographic area and may allowunrestricted access by UEs with service subscription. A femto cell maycover a relatively small geographic area (e.g., a home) and may allowrestricted access by UEs having association with the femto cell (e.g.,UEs in a closed subscriber group (CSG)). An eNB for a macro cell may bereferred to as a macro eNB. An eNB for a pico cell may be referred to asa pico eNB. An eNB for a femto cell may be referred to as a femto eNB ora home eNB (HeNB). In the example shown in FIG. 1, an eNB 110 a may be amacro eNB for a macro cell 102 a, an eNB 110 b may be a pico eNB for apico cell 102 b, and an eNB 110 c may be a femto eNB for a femto cell102 c. An eNB may support one or multiple (e.g., three) cells. The terms“eNB”, “base station,” and “cell” may be used interchangeably herein.

Wireless communication network 100 may also include relay stations. Arelay station is an entity that can receive a transmission of data froman upstream station (e.g., an eNB or a UE) and send a transmission ofthe data to a downstream station (e.g., a UE or an eNB). A relay stationmay also be a UE that can relay transmissions for other UEs. In theexample shown in FIG. 1, a relay (station) eNB 110 d may communicatewith macro eNB 110 a and a UE 120 d in order to facilitate communicationbetween eNB 110 a and UE 120 d. A relay station may also be referred toas a relay eNB, a relay base station, a relay, etc.

Wireless communication network 100 may be a heterogeneous network thatincludes eNBs of different types, e.g., macro eNBs, pico eNBs, femtoeNBs, relay eNBs, etc. These different types of eNBs may have differenttransmit power levels, different coverage areas, and different impact oninterference in wireless communication network 100. For example, macroeNBs may have a high transmit power level (e.g., 5 to 40 W) whereas picoeNBs, femto eNBs, and relay eNBs may have lower transmit power levels(e.g., 0.1 to 2 W).

A network controller 130 may couple to a set of eNBs and may providecoordination and control for these eNBs. Network controller 130 maycommunicate with the eNBs via a backhaul. The eNBs may also communicatewith one another, e.g., directly or indirectly via a wireless orwireline backhaul.

UEs 120 (e.g., 120 a, 120 b, 120 c) may be dispersed throughout wirelesscommunication network 100, and each UE may be stationary or mobile. A UEmay also be referred to as an access terminal, a terminal, a mobilestation (MS), a subscriber unit, a station (STA), etc. A UE may be acellular phone, a personal digital assistant (PDA), a wireless modem, awireless communication device, a handheld device, a laptop computer, acordless phone, a wireless local loop (WLL) station, a tablet, a smartphone, a netbook, a smartbook, an ultrabook, navigation devices, gamingdevices, cameras, a vehicular device, a drone, a robot/robotic device, awearable device (e.g., smart watch, smart clothing, smart wristband,smart ring, smart bracelet, smart glasses, virtual reality goggles), amedical device, a healthcare device, etc. MTC UEs include devices suchas sensors, meters, monitors, location tags, drones, trackers,robots/robotic devices, etc. UEs (e.g., MTC devices) may be implementedas internet of everything (IoE) or internet of things (IoT) (e.g.,narrowband IoT (NB-IoT)) devices.

One or more UEs 120 in the wireless communication network 100 (e.g., anLTE network) may also be low cost (LC), low data rate devices, e.g.,such as LC MTC UEs, LC eMTC UEs, etc. The LC UEs may co-exist withlegacy and/or advanced UEs in the LTE network and may have one or morecapabilities that are limited when compared to the other UEs (e.g.,non-LC UEs) in the wireless network. For example, when compared tolegacy and/or advanced UEs in the LTE network, the LC UEs may operatewith one or more of the following: a reduction in maximum bandwidth(relative to legacy UEs), a single receive radio frequency (RF) chain,reduction of peak rate, reduction of transmit power, rank 1transmission, half duplex operation, etc. As used herein, devices withlimited communication resources, such as MTC devices, eMTC devices, etc.are referred to generally as LC UEs. Similarly, legacy devices, such aslegacy and/or advanced UEs (e.g., in LTE) are referred to generally asnon-LC UEs.

FIG. 2 is a block diagram of a design of BS/eNB 110 and UE 120, whichmay be one of the BSs/eNBs 110 and one of the UEs 120, respectively, inFIG. 1. BS 110 may be equipped with T antennas 234 a through 234 t, andUE 120 may be equipped with R antennas 252 a through 252 r, where ingeneral T≥1 and R≥1.

At BS 110, a transmit processor 220 may receive data from a data source212 for one or more UEs, select one or more modulation and codingschemes (MCSs) for each UE based on channel quality indicators (CQIs)received from the UE, process (e.g., encode and modulate) the data foreach UE based on the MCS(s) selected for the UE, and provide datasymbols for all UEs. Transmit processor 220 may also process systeminformation (e.g., for semi-static resource partitioning information(SRPI), etc.) and control information (e.g., CQI requests, grants, upperlayer signaling, etc.) and provide overhead symbols and control symbols.Processor 220 may also generate reference symbols for reference signals(e.g., the common reference signal (CRS)) and synchronization signals(e.g., the primary synchronization signal (PSS) and secondarysynchronization signal (SSS)). A transmit (TX) multiple-inputmultiple-output (MIMO) processor 230 may perform spatial processing(e.g., precoding) on the data symbols, the control symbols, the overheadsymbols, and/or the reference symbols, if applicable, and may provide Toutput symbol streams to T modulators (MODs) 232 a through 232 t. EachMOD 232 may process a respective output symbol stream (e.g., for OFDM,etc.) to obtain an output sample stream. Each MOD 232 may furtherprocess (e.g., convert to analog, amplify, filter, and upconvert) theoutput sample stream to obtain a downlink signal. T downlink signalsfrom modulators 232 a through 232 t may be transmitted via T antennas234 a through 234 t, respectively.

At UE 120, antennas 252 a through 252 r may receive the downlink signalsfrom BS 110 and/or other BSs and may provide received signals todemodulators (DEMODs) 254 a through 254 r, respectively. Each DEMOD 254may condition (e.g., filter, amplify, downconvert, and digitize) itsreceived signal to obtain input samples. Each DEMOD 254 may furtherprocess the input samples (e.g., for OFDM, etc.) to obtain receivedsymbols. A MIMO detector 256 may obtain received symbols from all Rdemodulators 254 a through 254 r, perform MIMO detection on the receivedsymbols if applicable, and provide detected symbols. A receive processor258 may process (e.g., demodulate and decode) the detected symbols,provide decoded data for UE 120 to a data sink 260, and provide decodedcontrol information and system information to a controller/processor280. A channel processor may determine reference signal received power(RSRP), received signal strength indicator (RSSI), reference signalreceived quality (RSRQ), CQI, etc.

On the uplink, at UE 120, a transmit processor 264 may receive andprocess data from a data source 262 and control information (e.g., forreports comprising RSRP, RSSI, RSRQ, CQI, etc.) fromcontroller/processor 280. Processor 264 may also generate referencesymbols for one or more reference signals. The symbols from transmitprocessor 264 may be precoded by a TX MIMO processor 266 if applicable,further processed by MODs 254 a through 254 r (e.g., for SC-FDM, OFDM,etc.), and transmitted to BS 110. At BS 110, the uplink signals from UE120 and other UEs may be received by antennas 234, processed by DEMODs232, detected by a MIMO detector 236 if applicable, and furtherprocessed by a receive processor 238 to obtain decoded data and controlinformation sent by UE 120. Processor 238 may provide the decoded datato a data sink 239 and the decoded control information tocontroller/processor 240. BS 110 may include communication unit 244 andcommunicate to network controller 130 via communication unit 244.Network controller 130 may include communication unit 294,controller/processor 290, and memory 292.

Controllers/processors 240 and 280 may direct the operation at BS 110and UE 120, respectively. For example, controller/processor 240 and/orother processors and modules at BS 110 may perform or direct operationsillustrated in FIGS. 7, 11, 13 and/or other processes for the techniquesdescribed herein. Similarly, controller/processor 280 and/or otherprocessors and modules at UE 120 may perform or direct operationsillustrated in FIGS. 8, 12, 14 and/or processes for the techniquesdescribed herein. Memories 242 and 282 may store data and program codesfor BS 110 and UE 120, respectively. A scheduler 246 may schedule UEsfor data transmission on the downlink and/or uplink.

FIG. 3 shows an exemplary frame structure 300 for FDD in LTE. Thetransmission timeline for each of the downlink and uplink may bepartitioned into units of radio frames. Each radio frame may have apredetermined duration (e.g., 10 milliseconds (ms)) and may bepartitioned into 10 subframes with indices of 0 through 9. Each subframemay include two slots. Each radio frame may thus include 20 slots withindices of 0 through 19. Each slot may include L symbol periods, e.g.,seven symbol periods for a normal cyclic prefix (as shown in FIG. 3) orsix symbol periods for an extended cyclic prefix. The 2L symbol periodsin each subframe may be assigned indices of 0 through 2L−1.

In LTE, an eNB may transmit a primary synchronization signal (PSS) and asecondary synchronization signal (SSS) on the downlink in the center1.08 MHz of the system bandwidth for each cell supported by the eNB. ThePSS and SSS may be transmitted in symbol periods 6 and 5, respectively,in subframes 0 and 5 of each radio frame with the normal cyclic prefix,as shown in FIG. 3. The PSS and SSS may be used by UEs for cell searchand acquisition. The eNB may transmit a cell-specific reference signal(CRS) across the system bandwidth for each cell supported by the eNB.The CRS may be transmitted in certain symbol periods of each subframeand may be used by the UEs to perform channel estimation, channelquality measurement, and/or other functions. The eNB may also transmit aphysical broadcast channel (PBCH) in symbol periods 0 to 3 in slot 1 ofcertain radio frames. The PBCH may carry some system information. TheeNB may transmit other system information such as system informationblocks (SIBs) on a physical downlink shared channel (PDSCH) in certainsubframes. The eNB may transmit control information/data on a physicaldownlink control channel (PDCCH) in the first B symbol periods of asubframe, where B may be configurable for each subframe. The eNB maytransmit traffic data and/or other data on the PDSCH in the remainingsymbol periods of each subframe.

The PSS, SSS, CRS, and PBCH in LTE are described in 3GPP TS 36.211,entitled “Evolved Universal Terrestrial Radio Access (E-UTRA); PhysicalChannels and Modulation,” which is publicly available.

FIG. 4 shows two example subframe formats 410 and 420 for the downlinkwith a normal cyclic prefix. The available time frequency resources forthe downlink may be partitioned into resource blocks. Each resourceblock may cover 12 subcarriers in one slot and may include a number ofresource elements. Each resource element may cover one subcarrier in onesymbol period and may be used to send one modulation symbol, which maybe a real or complex value.

Subframe format 410 may be used for an eNB equipped with two antennas. ACRS may be transmitted from antennas 0 and 1 in symbol periods 0, 4, 7,and 11. A reference signal is a signal that is known a priori by atransmitter and a receiver and may also be referred to as pilot. A CRSis a reference signal that is specific for a cell, e.g., generated basedon a cell identity (ID). In FIG. 4, for a given resource element withlabel Ra, a modulation symbol may be transmitted on that resourceelement from antenna a, and no modulation symbols may be transmitted onthat resource element from other antennas. Subframe format 420 may beused for an eNB equipped with four antennas. A CRS may be transmittedfrom antennas 0 and 1 in symbol periods 0, 4, 7, and 11 and fromantennas 2 and 3 in symbol periods 1 and 8. For both subframe formats410 and 420, a CRS may be transmitted on evenly spaced subcarriers,which may be determined based on cell ID. Different eNBs may transmittheir CRSs on the same or different subcarriers, depending on their cellIDs. For both subframe formats 410 and 420, resource elements not usedfor the CRS may be used to transmit data (e.g., traffic data, controldata, and/or other data).

An interlace structure may be used for each of the downlink and uplinkfor FDD in LTE. For example, Q interlaces with indices of 0 through Q−1may be defined, where Q may be equal to 4, 6, 8, 10, or some othervalue. Each interlace may include subframes that are spaced apart by Qframes. In particular, interlace q may include subframes q, q+Q, q+2Q,etc., where q ∈ {0, . . . , Q−1}.

The wireless network may support hybrid automatic retransmission request(HARQ) for data transmission on the downlink and uplink. For HARQ, atransmitter (e.g., an eNB 110) may send one or more transmissions of apacket until the packet is decoded correctly by a receiver (e.g., a UE120) or some other termination condition is encountered. For synchronousHARQ, all transmissions of the packet may be sent in subframes of asingle interlace. For asynchronous HARQ, each transmission of the packetmay be sent in any subframe.

A UE may be located within the coverage of multiple eNBs. One of theseeNBs may be selected to serve the UE. The serving eNB may be selectedbased on various criteria such as received signal strength, receivedsignal quality, path loss, etc. Received signal quality may bequantified by a signal-to-interference-plus-noise ratio (SINR), or areference signal received quality (RSRQ), or some other metric. The UEmay operate in a dominant interference scenario in which the UE mayobserve high interference from one or more interfering eNBs.

As mentioned above, one or more UEs in the wireless communicationnetwork (e.g., wireless communication network 100) may be devices thathave limited communication resources, such as LC UEs, as compared toother (non-LC) devices in the wireless communication network.

In some systems, for example, in LTE Rel-13 and other releases, the LCUE may be limited to a particular narrowband assignment (e.g., of nomore than one resource block (RB) or no more than six RBs) within theavailable system bandwidth. However, the LC UE may be able to re-tune(e.g., operate and/or camp) to different narrowband regions within theavailable system bandwidth of the LTE system, for example, in order toco-exist within the LTE system.

As another example of coexistence within the LTE system, LC UEs may beable to receive (with repetition) legacy physical broadcast channel(PBCH) (e.g., the LTE physical channel that, in general, carriesparameters that may be used for initial access to the cell) and supportone or more legacy physical random access channel (PRACH) formats. Forexample, the LC UE may be able to receive the legacy PBCH with one ormore additional repetitions of the PBCH across multiple subframes. Asanother example, the LC UE may be able to transmit one or morerepetitions of PRACH (e.g., with one or more PRACH formats supported) toan eNB in the LTE system. The PRACH may be used to identify the LC UE.Also, the number of repeated PRACH attempts may be configured by theeNB.

The LC UE may also be a link budget limited device and may operate indifferent modes of operation (e.g. entailing different amounts ofrepeated messages transmitted to or from the LC UE) based on its linkbudget limitation. For example, in some cases, the LC UE may operate ina normal coverage mode in which there is little to no repetition (e.g.,the amount of repetition needed for the UE to successfully receiveand/or transmit a message may be low or repetition may not even beneeded). Alternatively, in some cases, the LC UE may operate in acoverage enhancement (CE) mode in which there may be high amounts ofrepetition. For example, for a 328 bit payload, a LC UE in CE mode mayneed 150 or more repetitions of the payload in order to successfullyreceive the payload.

In some cases, e.g., also for LTE Rel-13, the LC UE may have limitedcapabilities with respect to its reception of broadcast and unicasttransmissions. For example, the maximum transport block (TB) size for abroadcast transmission received by the LC UE may be limited to 1000bits. Additionally, in some cases, the LC UE may not be able to receivemore than one unicast TB in a subframe. In some cases (e.g., for boththe CE mode and normal mode described above), the LC UE may not be ableto receive more than one broadcast TB in a subframe. Further, in somecases, the LC UE may not be able to receive both a unicast TB and abroadcast TB in a subframe.

For MTC, LC UEs that co-exist in the LTE system may also support newmessages for certain procedures, such as paging, random accessprocedure, etc. (e.g., as opposed to conventional messages used in LTEfor these procedures). In other words, these new messages for paging,random access procedure, etc. may be separate from the messages used forsimilar procedures associated with non-LC UEs. For example, as comparedto conventional paging messages used in LTE, LC UEs may be able tomonitor and/or receive paging messages that non-LC UEs may not be ableto monitor and/or receive. Similarly, as compared to conventional randomaccess response (RAR) messages used in a conventional random accessprocedure, LC UEs may be able to receive RAR messages that also may notbe able to be received by non-LC UEs. The new paging and RAR messagesassociated with LC UEs may also be repeated one or more times (e.g.,“bundled”). In addition, different numbers of repetitions (e.g.,different bundling sizes) for the new messages may be supported.

As mentioned above, MTC and/or eMTC operation may be supported in thewireless communication network (e.g., in coexistence with LTE or someother RAT). FIGS. 5A and 5B, for example, illustrate an example of howLC UEs in MTC operation may co-exist within a wideband system, such asLTE.

As illustrated in the example frame structure of FIG. 5A, subframes 510associated with MTC and/or eMTC operation may be time divisionmultiplexed (TDM) with regular subframes 520 associated with LTE (orsome other RAT).

Additionally or alternatively, as illustrated in the example framestructure of FIG. 5B, one or more narrowband regions 560, 562 used by LCUEs in MTC may be frequency division multiplexed within the widerbandwidth 550 supported by LTE. Multiple narrowband regions, with eachnarrowband region spanning a bandwidth that is no greater than a totalof 6 RBs, may be supported for MTC and/or eMTC operation. In some cases,each LC UE in MTC operation may operate within one narrowband region(e.g., at 1.4 MHz or 6 RBs) at a time. However, LC UEs in MTC operation,at any given time, may re-tune to other narrowband regions in the widersystem bandwidth. In some examples, multiple LC UEs may be served by thesame narrowband region. In other examples, multiple LC UEs may be servedby different narrowband regions (e.g., with each narrowband regionspanning 6 RBs). In yet other examples, different combinations of LC UEsmay be served by one or more same narrowband regions and/or one or moredifferent narrowband regions.

The LC UEs may operate (e.g., monitor/receive/transmit) within thenarrowband regions for various different operations. For example, asshown in FIG. 5B, a first narrowband region 560 (e.g., spanning no morethan 6 RBs of the wideband data) of a subframe 552 may be monitored byone or more LC UEs for either a PSS, SSS, PBCH, MTC signaling, or pagingtransmission from a BS in the wireless communication network. As alsoshown in FIG. 5B, a second narrowband region 562 (e.g., also spanning nomore than 6 RBs of the wideband data) of a subframe 554 may be used byLC UEs to transmit a RACH or data previously configured in signalingreceived from a BS. In some cases, the second narrowband region may beutilized by the same LC UEs that utilized the first narrowband region(e.g., the LC UEs may have re-tuned to the second narrowband region totransmit after monitoring in the first narrowband region). In some cases(although not shown), the second narrowband region may be utilized bydifferent LC UEs than the LC UEs that utilized the first narrowbandregion.

Although the examples described herein assume a narrowband of 6 RBs,those skilled in the art will recognize that the techniques presentedherein may also be applied to different sizes of narrowband regions (forexample, 1 RB, supported by NB-IoT).

As mentioned above, in certain systems, e.g., such as LTE Rel-12,narrowband operation for MTC (e.g., eMTC) may be supported. A cellsupporting narrowband operation for MTC may have different systembandwidths for downlink (DL) and uplink (UL) operations. A cell havingdifferent DL and UL system bandwidths (SBs) may organize the DL systembandwidth into narrowband regions in a manner different than the mannerused to organize the UL system bandwidth into narrowband regions.Accordingly, aspects of the present disclosure provide techniques fororganizing a DL system bandwidth and an UL system bandwidth intonarrowband regions.

A cell supporting narrowband operation for MTC and legacy UEs mayreceive legacy PUCCH transmissions from the legacy UEs. Legacy PUCCHtransmissions may be transmitted at either or both edges of a UL systembandwidth of a cell. Accordingly, aspects of the present disclosureprovide techniques to reserve transmission resources included in an ULnarrowband region for use by legacy PUCCH transmissions. Similarreservations may also be applied to a DL narrowband region for use byother legacy DL signals or channels.

A cell supporting narrowband operations for MTC may also supporttransmission of sounding reference signals (SRS). The current minimumdefined bandwidth for transmission of SRS is four RBs. However, asmentioned above, the bandwidth of narrowband regions is six RBs. Thefact that six RBs are not divisible by four RBs presents challenges inmanaging SRS transmissions using four RBs in six-RB based narrowbandoperations. Accordingly, aspects of the present disclosure providetechniques for assigning transmission resources for transmission of SRSin a cell supporting narrowband operations (e.g., for MTC).

A cell operating with FDD may have a DL system bandwidth that is of adifferent size than the UL system bandwidth of the cell. For example, acell may perform DL operations in a system bandwidth of ten MHz and ULoperations in a five MHz system bandwidth. To support MTC operations andMTC UEs, the cell may organize the DL system bandwidth and the UL systembandwidth into narrowband regions, or narrowband regions. An eNB orother BS controlling the cell may assign a DL narrowband region to a MTCUE for the MTC UE to monitor for signals from the eNB. Similarly, theeNB (or other BS) may assign a UL narrowband region to the MTC UE forthe MTC to use when transmitting UL signals. In the example, the cellmay organize the DL system bandwidth into eight DL narrowband regionswhile organizing the UL system bandwidth into four UL narrowbandregions.

When a BS (e.g., an eNB or a cell) supports MTC UEs with the DL systembandwidth and UL system bandwidth of the cell organized into narrowbandregions, the BS may establish a mapping between DL narrowband regionsand UL narrowband regions, so that assigning a DL narrowband region toan MTC UE implies an assignment of a UL narrowband region to that MTCUE. Having a mapping allows the BS to simplify scheduling of resourcesin the cell, e.g., the BS can expect ACK/NAKs for transmissions on a DLnarrowband region to an MTC UE on the corresponding UL narrowbandregion. Likewise, an MTC UE monitors for DL transmissions on theassigned DL narrowband region for the MTC UE and responds withtransmissions on the corresponding UL narrowband region.

According to aspects of the present disclosure, a technique for mappingUL and DL narrowband regions by a BS is provided. A BS may determine aminimum size of the UL system bandwidth and the DL system bandwidthsupported by the BS, determine a number of narrowband regions that canbe organized in the determined size, and then organize both the DLsystem bandwidth and the UL system bandwidth in that number ofnarrowband regions. The BS may then map each DL narrowband region to oneUL narrowband region. For example, a cell may perform DL operations in asystem bandwidth of ten MHz and UL operations in a five MHz systembandwidth. In the example, the BS may determine that the minimum size ofthe UL system bandwidth and the DL system bandwidth is five MHz, andthen determine that the BS can organize four narrowband regions in afive MHz system bandwidth. Still in the example, the BS may thenorganize four DL narrowband regions in the DL system bandwidth and fourUL narrowband regions in the UL system bandwidth, and map each DLnarrowband region to one UL narrowband region.

FIG. 6 illustrates an exemplary mapping 600 of DL narrowband regions toUL narrowband regions, as described above. Such a mapping may beemployed by eNB 110 a in FIG. 1. While FIG. 6 shows the DL systembandwidth 610 and the UL system bandwidth 650 as apparently in the samefrequency ranges, the DL system bandwidth and the UL system bandwidthare in different frequency ranges in a cell using FDD. DL systembandwidth 610 is ten MHz or fifty RBs wide, and UL system bandwidth 650is five MHz or twenty-five RBs wide. A BS supporting MTC UEs whileoperating DL system bandwidth 610 and UL system bandwidth 650 maydetermine that the UL system bandwidth 650 is smaller than DL systembandwidth 610 (the 5 MHz size of UL system bandwidth 650 is the minimumsize of the UL system bandwidth 650 and the DL system bandwidth 610).The BS may then determine that the BS can organize four narrowbandregions 652, 654, 656, and 658 from the UL system bandwidth 650. The BSmay then determine to organize four narrowband regions from the DLsystem bandwidth, and organize DL narrowband regions 612, 614, 616, and618 from the DL system bandwidth. The BS may then map DL narrowbandregion 612 to UL narrowband region 652, DL narrowband region 614 to ULnarrowband region 654, DL narrowband region 616 to UL narrowband region656, and DL narrowband region 618 to UL narrowband region 658.

As mentioned above, LC MTC UEs were introduced in LTE Rel-12. Additionalenhancements may be made in LTE Release 13 (Rel-13) to support eMTCoperations. For example, MTC UEs may be able to operate (e.g., monitor,transmit, and receive) in a narrowband region of 1.4 MHz or six RBswithin wider system bandwidths (e.g., 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15MHz, 20 MHz). As a second example, base stations and MTC UEs may supportcoverage enhancements (CE) of up to 15 dB by some techniques, forexample bundling. Coverage enhancement may also be referred to ascoverage extension and range extension.

Other enhancements that may be made in LTE Rel-13 may include basestations transmitting paging signals in MTC physical downlink controlchannels (MPDCCHs) in a narrowband in order to page MTC UEs. An MPDCCHmay convey paging signals for multiple MTC UEs and a downlink controlinformation (DCI) to one or more other MTC UEs. MPDCCH may be similar toPDCCH/EPDCCH as described above. Demodulation reference signal (DM-RS)based demodulation may be supported when using MPDCCH. That is, a BStransmitting an MPDCCH may transmit DM-RS with the MPDCCH. A UEreceiving the MPDCCH and DM-RS may demodulate the MPDCCH based on theDM-RS.

Enhancements that may be made in LTE Rel-13 may also include BSstransmitting random access response (RAR) signals in an MPDCCH in anarrowband in order to respond to physical random access channel (PRACH)signals from MTC UEs. A BS may send a single RAR message in a DCI in anMPDCCH or multiple RAR messages (e.g., to respond to multiple UEs) in anMPDCCH without a DCI.

A UE that has an active receiver (e.g., the receiver is not powereddown) typically monitors for PDCCH (e.g., EPDCCH, MPDCCH) in one or moresearch spaces. The UE typically monitors at least one common searchspace and may be configured to monitor a UE-specific search space. Asearch space includes a set of groups of contiguous control channelelements (CCE). The UE uses an identifier (e.g., a radio networktemporary identifier (RNTI)) of the UE in determining if any one of thegroups in the search space contains a PDCCH directed at the UE.Monitoring for PDCCHs is further described in 3GPP TS 36.213 “EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical layer procedures,”which is publicly available and hereby incorporated by reference.

FIG. 7 illustrates example operation 700 for wireless communicationsthat may be performed by a BS (e.g., eNodeB 110 a in FIG. 1), accordingto aspects of the present disclosure described above. The operation 700may be performed by a BS to support MTC UEs, and may use one of theexemplary techniques illustrated in FIGS. 9-10 below.

Operation 700 begins at block 702, wherein the BS receives a physicalrandom access channel (PRACH) signal from a first user equipment (UE) ona first narrowband region within a wider system bandwidth. Operation 700continues at block 704, wherein the BS transmits, in response to thePRACH signal, a random access response (RAR) message in a first searchspace in a second narrowband region in at least a first subframe.

According to aspects of the present disclosure, a BS (e.g., the BSmentioned in FIG. 7) may transmit a paging signal in a second searchspace in a third narrowband region. That is, a BS may transmit pagingsignals in narrowband regions other than the narrowband regions used forPRACHs and RAR messages.

According to aspects of the present disclosure, a BS (e.g., the BSmentioned in FIG. 7) may identify a third search space in a fourthnarrowband region for transmitting RAR messages to a second UE with adifferent coverage enhancement (CE) level than the first UE. The BS mayalso transmit information regarding the first search space and a firstCE level for the first search space in a system information block (SIB)and transmit information regarding the third search space and a secondCE level for the third search space in at least one of the SIB oranother SIB. That is, a BS may transmit information regarding searchspaces and CE levels in one or more SIBs.

According to aspects of the present disclosure, a BS (e.g., the BSmentioned in FIG. 7) may transmit information regarding the first searchspace in a SIB. For example, a BS that does not differentiate between CElevels may broadcast information regarding a search space in a SIB.

According to aspects of the present disclosure, a BS (e.g., the BSmentioned in FIG. 7) may determine a RAR response window, a set ofmachine type communications (MTC) physical downlink control channel(MPDCCH) starting point subframes, a RAR offset number of subframes, anda bundle size for each of a plurality of coverage enhancement (CE)levels. That is, a BS may use different RAR response windows, MPDCCHstarting point subframes, RAR offset numbers, and bundle sizes fordifferent CE levels, and the BS may determine those various RAR responsewindows, MPDCCH starting point subframes, RAR offset numbers, and bundlesizes for the different CE levels.

According to aspects of the present disclosure, a BS (e.g., the BSmentioned in FIG. 7) may determine a radio frequency for paging, a timefor paging, a bundle size for paging, and a set of monitoring candidatesbased at least on a maximum coverage enhancement (CE) level supported bythe BS.

According to aspects of the present disclosure, a BS (e.g., the BSmentioned in FIG. 7) may refrain from transmitting a dedicated channelto the first UE during at least a second subframe and transmit at leastone system information (SI) change or earthquake and tsunami warningsystem (ETWS) signal in a broadcast channel of the wider systembandwidth during at least the second subframe.

FIG. 8 illustrates example operation 800 for wireless communicationsthat may be performed by a UE (e.g., UE 120 a in FIG. 1), according toaspects of the present disclosure. The operation 800 may be performed byan MTC UE, for example, and may use one of the exemplary techniquesillustrated in FIGS. 9-10 below. The operation 800 may be consideredcomplimentary to the operation 700 in FIG. 7 described above.

Operation 800 begins at block 802, wherein the UE transmits a physicalrandom access channel (PRACH) signal to a base station (BS) on a firstnarrowband region within a wider system bandwidth. Operation 800continues at block 804, wherein the UE receives, in response to thePRACH signal, a random access response (RAR) message in a first searchspace in a second narrowband region in at least a first subframe.

According to aspects of the present disclosure, an MTC UE may beconfigured with an MPDCCH common search space (e.g., the first searchspace mentioned in block 804 above) within a narrowband region of awider system bandwidth. A BS serving MTC UEs may be configured totransmit MPDCCHs conveying paging signals and RAR messages in an MPDCCHcommon search space (e.g., the first search space mentioned in block 704above) within a narrowband region of a wider system bandwidth.

According to aspects of the present disclosure, a BS may transmit pagingsignals and RAR messages (e.g., the RAR message mentioned in block 804above) in MPDCCHs within an MPDCCH common search space, according toaspects of the present disclosure. A BS transmitting MPDCCHs within anMPDCCH common search space may multiplex paging and RAR messages withinthe MPDCCHs.

According to aspects of the present disclosure, a UE (e.g., the UEmentioned in FIG. 8) may identify a third search space in a fourthnarrowband region for receiving RAR messages based at least in part on acoverage enhancement (CE) level of the UE, receive information regardingthe first search space and a first CE level for the first search spacein a system information block (SIB), and receive information regardingthe third search space and a second CE level for the third search spacein at least one of the SIB or another SIB.

According to aspects of the present disclosure, a UE (e.g., the UEmentioned in FIG. 8) may determine a RAR response window, a set ofmachine type communications (MTC) physical downlink control channel(MPDCCH) starting point subframes, a RAR offset number of subframes, anda bundle size for each of a plurality of coverage enhancement (CE)levels.

According to aspects of the present disclosure, a UE (e.g., the UEmentioned in FIG. 8) may determine a radio frequency for paging, a timefor paging, a bundle size for paging, and a set of monitoring candidatesbased at least on a maximum coverage enhancement (CE) level supported bythe BS. The UE may also receive information regarding the maximum CElevel supported by the BS (e.g., in a SIB transmitted by the BS).

According to aspects of the present disclosure, a UE (e.g., the UEmentioned in FIG. 8) may receive at least one of a system information(SI) change or earthquake and tsunami warning system (ETWS) signal inthe second narrowband region.

According to aspects of the present disclosure, a UE (e.g., the UEmentioned in FIG. 8) may receive at least one SI change or ETWS signalin a broadcast channel of the wider system bandwidth during at least asecond subframe.

FIG. 9 illustrates exemplary techniques 910, 920, and 930 formultiplexing MPDCCHs conveying paging signals with MPDCCHs conveying RARmessages. In exemplary technique 910, an MPDCCH 912 conveying a RARmessage is frequency division multiplexed with an MPDCCH 914 conveying apaging signal. While the exemplary technique shows the MPDCCHs bundledover K subframes (SF), the disclosure is not so limited and the MPDCCHsmay be multiplexed in a single subframe. In exemplary technique 920, anMPDCCH 922 conveying a RAR message is time division multiplexed with anMPDCCH 924 conveying a paging signal. The technique shows each MPDCCHbundled over K subframes (SF), but the disclosure is not so limited andeach MPDCCH may be transmitted in a single subframe. In exemplarytechnique 930, an MPDCCH 932 conveying a RAR message is time divisionmultiplexed with an MPDCCH 934 conveying a paging signal, but eachMPDCCH is conveyed in a non-continuous bundle 936, 938. That is, eachMPDCCH is bundled over a plurality (e.g., 2, 4, 8) of subframes, buteach of the bundles includes subframes that are not all consecutive.

When a BS pages a UE operating in a coverage enhancement (CE) level ofmore than 0 dB (e.g., 3 dB, 15 dB), the BS may transmit a plurality orbundle of MPDCCHs conveying paging signals in a plurality of subframes(e.g., the bundles illustrated in techniques 910, 920, and 930 in FIG. 9above) to the UE. The subframes may be continuous or non-continuous.That is, the BS may transmit MPDCCHs in consecutive subframes, in groupsof consecutive subframes with subframes between the groups, or innon-consecutive subframes. The paged UE may receive the MPDCCHs in thebundle of subframes, combine the paging signals, and decode thecombination. Combining the MPDCCHs may increase the probability of theUE successfully decoding the MPDCCH and detecting the paging signal.

A BS configured to support UEs with a CE level above 0 dB may signal,for example in a system information block (SIB) or via radio resourcecontrol, information regarding a bundling technique(s) (e.g., techniques910, 920, and/or 930 in FIG. 9 above) used by the BS when paging UEs.Such information may include, for example, a starting subframe of apaging occasion and a repetition pattern for the paging occasion. A UEsupported by the BS may receive the information and determine whichsubframes contain MPDCCHs to combine when attempting to decode anMPDCCH. A UE may use the information regarding the bundling technique(s)to determine subframes containing MPDCCHs and combine signals receivedin the subframes before attempting to decode the MPDCCH.

A UE receiving an MPDCCH time division multiplexed using non-continuousbundles (e.g., as illustrated in exemplary technique 930 in FIG. 9above) may correctly decode an MPDCCH without waiting to receive theentire bundle. This may happen in situations when a transmitting BS isconfigured to support a CE level higher than the CE level under whichthe receiving UE is operating. For example, a BS supporting a CE levelof 15 dB may bundle each MPDCCH in ten subframes. In the example, areceiving UE that is in good signal conditions and operating under a CElevel of 0 dB may decode an MPDCCH after receiving a first subframe ofthe ten-subframe bundle.

FIG. 10 illustrates exemplary techniques 1010, 1020, and 1030 forconfiguring MPDCCH common search space for MPDCCHs conveying pagingsignals and one or more MPDCCH common search spaces for MPDCCHsconveying RAR messages, according to aspects of the present disclosuredescribed above. In exemplary technique 1010, an MPDCCH common searchspace 1012 for MPDCCHs conveying RAR messages is configured on a firstnarrowband region and an MPDCCH common search space 1014 for MPDCCHsconveying paging signals is configured on a second narrowband region.

In exemplary technique 1020, a first MPDCCH common search space 1022 forMPDCCHs conveying RAR messages is configured on a first narrowbandregion, a second MPDCCH common search space 1024 for MPDCCHs conveyingRAR messages is configured on a second narrowband region, and an MPDCCHcommon search space 1026 for MPDCCHs conveying paging signals isconfigured on a third narrowband region. The first MPDCCH common searchspace 1022 for MPDCCHs conveying RAR messages is used to respond toPRACH signals of bundle size #1, while the second MPDCCH common searchspace 1024 for MPDCCHs conveying RAR messages is used to respond toPRACH signals of bundle size #2. The technique shows two MPDCCH commonsearch spaces for MPDCCHs conveying RAR messages, but the disclosure isnot so limited and may be used with more MPDCCH common search spaces.

In exemplary technique 1030, a first MPDCCH common search space 1032 forMPDCCHs conveying RAR messages is configured on a first narrowbandregion, a second MPDCCH common search space 1034 for MPDCCHs conveyingRAR messages is configured on a second narrowband region, and an MPDCCHcommon search space 1036 for MPDCCHs conveying paging signals isconfigured on a third narrowband region, similar to exemplary technique1020. The first MPDCCH common search space 1032 for MPDCCHs conveyingRAR messages is used to respond to PRACH signals received on narrowbandregion or subband #1, while the second MPDCCH common search space 1034for MPDCCHs conveying RAR messages is used to respond to PRACH signalsreceived on narrowband region or subband #2. The technique shows twoMPDCCH common search spaces for MPDCCHs conveying RAR messages, but thedisclosure is not so limited and may be used with more MPDCCH commonsearch spaces.

According to aspects of the present disclosure, a BS serving MTC UEs maybe configured to transmit MPDCCHs conveying paging signals in a firstMPDCCH common search space and MPDCCHs conveying RAR messages in asecond MPDCCH common search space in first and second narrowband regionsof a wider system bandwidth (e.g., as in exemplary technique 1010 inFIG. 10 above).

A BS may be configured with a plurality of MPDCCH common search spacesfor MPDCCHs conveying RAR messages. The BS may determine which MPDCCHcommon search space to use for transmitting a RAR message based on thePRACH signal to which the RAR message is responsive (e.g., as intechnique 1020 in FIG. 10 above). The BS may determine to transmit a RARmessage in a first MPDCCH common search space if the BS received a PRACHsignal bundled in x (e.g., two) or fewer subframes (corresponding to aCE level of y or less for the transmitting UE), and the BS may determineto transmit the RAR message in a second MPDCCH common search space ifthe BS received a PRACH signal bundled in x+1 (e.g., three) or moresubframes (corresponding to a CE level more than y for the transmittingUE). A BS configured with more than two MPDCCH common search spaces forconveying RAR messages may be configured to use each MPDCCH commonsearch space for responding to PRACH signals in different PRACH signalbundle size ranges.

Additionally or alternatively, a BS configured with a plurality ofMPDCCH common search spaces for conveying RAR messages may determinewhich MPDCCH common search space to use for transmitting a RAR messagebased on a subband used for transmitting the PRACH signal to which theRAR message is responsive (e.g., as in technique 1030 in FIG. 10 above).The BS may determine to transmit a RAR message in a first MPDCCH commonsearch space if the BS received a PRACH signal on a first narrowbandregion or subband, and the BS may determine to transmit the RAR messagein a second MPDCCH common search space if the BS received a PRACH signalon a second narrowband region or subband. A BS configured with more thantwo MPDCCH common search spaces for conveying RAR messages may beconfigured to use each MPDCCH common search space for responding toPRACH signals in a different narrowband region.

According to aspects of the present disclosure, a BS may transmitinformation regarding which MPDCCH common search space the BS will usefor transmitting MPDCCHs conveying RAR messages based on the bundle sizeor CE level of the PRACH signal to which the RAR message is responsive.That is, a BS may transmit a signal indicating that PRACH signals of afirst bundle size or first CE level or smaller will be responded to (bythe BS) with RAR messages in a first MPDCCH common search space, andPRACH signals of a bundle size larger than the first bundle size or CElevel larger than the first CE level will be responded to with RARmessages in a second MPDCCH common search space. The information may betransmitted, for example, in a system information block (SIB). If a BSis configured with more than two MPDCCH common search spaces for morethan two bundle sizes or CE levels, the BS may transmit informationregarding all of the MPDCCH common search spaces, bundle sizethresholds, and CE level thresholds.

According to aspects of the present disclosure, an MTC UE may beconfigured with a first MPDCCH common search space in a first narrowbandregion for MPDCCHs conveying RAR messages (e.g., as in operation 800 inFIG. 8 above). The MTC UE may transmit a PRACH signal to a BS on asecond narrowband region. The UE may receive an MPDCCH conveying a RARmessage from the BS in the first MPDCCH common search space. The UE mayreceive information regarding the first MPDCCH common search space forMPDCCHs conveying RAR messages in a system information block (SIB).

According to some aspects of the present disclosure, a UE may receive anMPDCCH conveying a paging signal multiplexed (e.g., as in technique 910in FIG. 9 above) with the MPDCCH conveying the RAR message in the firstMPDCCH common search space in at least one subframe.

A UE may receive an MDPCCH conveying a paging signal in the first MPDCCHcommon search space in another subframe (e.g., as in technique 920 inFIG. 9 above). According to aspects of the present disclosure, theMPDCCH conveying the RAR message may be bundled in non-continuoussubframes and the MPDCCH conveying the paging signal may be bundled innon-continuous subframes (e.g., as in technique 930 in FIG. 9 above).

An MTC UE may be configured with a first MPDCCH common search space forMPDCCHs conveying paging signals and a second MPDCCH common search spacefor MPDCCHs conveying RAR messages (e.g., as in technique 1010 in FIG.10 above). The first and second MPDCCH common search spaces may each bewithin different narrowband regions of a wider system bandwidth.

An MTC UE may identify a third MPDCCH common search space for MPDCCHsconveying RAR messages (e.g., as in technique 1020 in FIG. 10 above).The UE may determine to monitor the second MPDCCH common search spacefor MPDCCHs conveying RAR messages or the third MPDCCH common searchspace for MPDCCHs conveying RAR messages based on a coverage enhancement(CE) level of the UE. The UE may receive information regarding thesecond MPDCCH common search space for MPDCCHs conveying RAR messages andthe corresponding CE level in a system information block (SIB). The UEmay also receive information regarding the third MPDCCH common searchspace for MPDCCHs conveying RAR messages and the corresponding CE levelin a SIB.

An MTC UE may identify a third MPDCCH common search space for MPDCCHsconveying RAR messages (e.g., as in technique 1030 in FIG. 10 above).The UE may determine to monitor the second MPDCCH common search spacefor MPDCCHs conveying RAR messages or the third MPDCCH common searchspace for MPDCCHs conveying RAR messages based on the narrowband regionor subband used for transmitting the PRACH signal. The UE may receiveinformation regarding the second MPDCCH common search space for MPDCCHsconveying RAR messages and the corresponding PRACH subband in a systeminformation block (SIB). The UE may also receive information regardingthe third MPDCCH common search space for MPDCCHs conveying RAR messagesand the corresponding PRACH subband in a SIB.

A BS may determine whether to multiplex MPDCCHs conveying paging signalsand MPDCCHs conveying RAR messages in the same subframes in one MPDCCHcommon search space as illustrated in technique 910 shown in FIG. 9, orto transmit MPDCCHs conveying paging signals and MPDCCHs conveying RARmessages using other techniques. A BS supporting only low CE levels orbundle sizes may determine to multiplex MPDCCHs conveying paging signalsand MPDCCHs conveying RAR messages. A BS supporting higher CE levels(e.g., 15 dB) or bundle sizes (e.g., 10 subframes) may determine to timedivision multiplex MPDCCHs conveying paging signals and MPDCCHsconveying RAR messages as illustrated in technique 920 shown in FIG. 9.Alternatively the BS supporting the higher CE levels or bundle sizes maydetermine to transmit MPDCCHs conveying paging signals in a first MPDCCHcommon search space and to transmit MPDCCHs conveying RAR messages inone or more other MPDCCH common search spaces as in techniques 1020 and1030 shown in FIG. 10.

According to aspects of the present disclosure, a BS may transmit anindication of a RAR response window for each of a plurality of CElevels. A RAR response window is a period of time that a UE shouldmonitor for RAR messages after transmitting a PRACH signal beforedetermining that the UE should transmit a PRACH signal. A BS maytransmit an indication of a RAR offset number of subframes or RARresponse window for each of the plurality of CE levels. A RAR offset isa period of time that a UE should wait after finishing PRACHtransmission before beginning monitoring for RAR messages for the RARresponse window. An MTC UE may have a RAR offset longer than a standardUE due, for example, to retuning time or half duplex capability.

A BS may transmit an indication of a set of MPDCCH starting pointsubframes for each of the plurality of CE levels. The set of MPDCCHstarting point subframes are the subframes in which the BS may begintransmitting an MPDCCH (e.g., the first subframe of a bundle ofsubframes). A BS may transmit an indication of a bundle size for each ofthe plurality of CE levels.

According to aspects of the present disclosure, a BS may determine aradio frequency for paging, a time for paging, and a bundle size forMPDCCHs conveying paging signals, based on a maximum CE level supportedby the BS.

According to aspects of the present disclosure, a BS may transmit asystem information (SI) change or earthquake and tsunami warning system(ETWS) signal in a broadcast channel of the wider system bandwidth. TheBS may transmit the same SI change or ETWS signal in dedicated signalingto one or more MTC UEs in narrowband regions, because connected mode(e.g., not idle mode) UEs may not monitor the broadcast channels of thewider system bandwidth.

According to aspects of the present disclosure, an MTC UE that is inconnected mode may periodically tune away from the narrowband regionassigned to the MTC UE and tune to the broadcast region of the widersystem bandwidth. A BS supporting the MTC UE may determine time periodsthat the MTC UE tunes away from the narrowband region assigned to theMTC UE and refrain from transmitting any dedicated channels to the UE.The BS may transmit a system information (SI) change or earthquake andtsunami warning system (ETWS) signal to the MTC UE in a broadcastchannel of the wider system bandwidth in time periods that the MTC UEhas tuned away from the narrowband region assigned to the MTC UE toimprove the probability that the MTC UE will receive the SI changeand/or the ETWS signal.

According to aspects of the present disclosure, a BS serving a UE (e.g.,an MTC UE) with the UE in connected mode (e.g., connected DRX mode) maycause the UE to transition to a disconnected mode. The BS may cause theUE to transition to a disconnected mode by, for example, sending anexplicit command to disconnect or by refraining from responding totransmissions from the UE, which may cause the UE to declare a radiolink failure (RLF) and disconnect from the BS. The BS may cause the UEto transition to a disconnected mode so that the UE may monitor pagingchannels to receive notifications of an SI change and/or an ETWS signal.

FIG. 11 illustrates example operation 1100 for wireless communicationsthat may be performed by a BS (e.g., eNodeB 110 a in FIG. 1), accordingto aspects of the present disclosure. The operation 1100 may beperformed by a BS to scramble transmissions to and otherwise support MTCUEs.

Operation 1100 begins at block 1102, wherein the BS determines acoverage enhancement (CE) level of a UE. Operation 1100 continues atblock 1104, wherein the BS initializes a scrambling sequence fortransmitting a signal to the UE based on the CE level. At block 1106,the BS scrambles the signal to the UE with the scrambling sequence. Atblock 1108, operation 1100 continues with the BS transmitting thescrambled signal to the UE.

FIG. 12 illustrates example operation 1200 for wireless communicationsthat may be performed by a UE (e.g., UE 120 a in FIG. 1), according toaspects of the present disclosure. The operation 1200 may be performedby an MTC UE to descramble an MPDCCH, for example. The operation 1200may be considered complementary to the operation 1100 in FIG. 11described above.

Operation 1200 begins at block 1202, wherein the UE initializes ascrambling sequence based on a coverage enhancement (CE) level of theUE. Operation 1200 continues at block 1204, wherein the UE receives asignal scrambled with the scrambling sequence. At block 1206, the UEdescrambles the signal with the scrambling sequence.

FIG. 13 illustrates example operation 1300 for wireless communicationsthat may be performed by a BS (e.g., eNodeB 110 a in FIG. 1), accordingto aspects of the present disclosure. The operation 1300 may beperformed by a BS to scramble transmissions to and otherwise support MTCUEs.

Operation 1300 begins at block 1302, wherein the BS scrambles a firstdemodulation reference signal (DM-RS) to a first UE with a scramblingsequence initialized with a scrambling sequence initialization.Operation 1300 continues at block 1304, wherein the BS scrambles asecond DM-RS to a second UE with a second scrambling sequenceinitialized with the scrambling sequence initialization. At block 1306,the BS transmits the scrambled first DM-RS to the first UE and thescrambled second DM-RS to the second UE in a same search space.

FIG. 14 illustrates example operation 1400 for wireless communicationsthat may be performed by a UE (e.g., UE 120 a in FIG. 1), according toaspects of the present disclosure. The operation 1400 may be performedby an MTC UE to descramble an MPDCCH, for example. The operation 1400may be considered complementary to the operation 1300 in FIG. 13described above.

Operation 1400 begins at block 1402, wherein the UE receives a firstdemodulation reference signal (DM-RS) scrambled with a scramblingsequence initialized with a scrambling sequence initialization.Operation 1400 continues at block 1404, wherein the UE receives a signalscrambled with the first scrambling sequence in a search space, whereinat least a second DM-RS scrambled with a second scrambling sequenceinitialized with the scrambling sequence initialization is transmittedin the search space. At block 1406, the UE descrambles the signal withthe scrambling sequence.

According to aspects of the present disclosure, a BS supporting MTC UEsmay use a fixed scrambling ID when scrambling MPDCCHs (e.g., as inoperation 1100 in FIG. 11 above) or MPDCCH associated reference signals(e.g., DM-RS) to be transmitted in an MPDCCH common search space. Thescrambling ID is fixed so that all UEs receiving the MPDCCH may be ableto descramble the MPDCCH. The fixed scrambling ID may be transmitted ina SIB (e.g., SIB1).

Scrambling of MPDCCHs may be similar to scrambling of EPDCCHs asdescribed in 3GPP TS 36.213 “Evolved Universal Terrestrial Radio Access(E-UTRA); Physical layer procedures” and 3GPP TS 36.211 “EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical Channels andModulation,” which are publicly available and hereby incorporated byreference. The variable Y_(p,k) used to determine the MPDCCH decodingcandidates is initialized with either the paging radio network temporaryidentifier (P-RNTI) or the random access radio network temporaryidentifier (RA-RNTI), depending on whether the MPDCCH conveys a pagingsignal or a RAR message. In some cases, the MPDCCH decoding candidatesmay be determined by the maximum coverage enhancement level supported bya BS, which may be signaled in a SIB1 transmitted by the BS. As notedabove, the scrambling ID n^(MPDCCH) _(SCID) is fixed for all UEs servedby a cell. In order to improve randomization between EPDCCH and MPDCCH,the scrambling ID may be set to 3, which differs from the scrambling IDfor EPDCCH n^(EPDCCH) _(ID,m) that is typically set to 2. The scramblinginitialization for MPDCCH is then:c _(init)=(└n _(s)/2┘+1)·(2n ^(EPDCCH) _(ID,i)+1)·2¹⁶ +n ^(MPDCCH)_(SCID)

The scrambling ID can depend on the CE levels of UEs being signaled. Forexample, a BS may use n^(MPDCCH) _(SCID)=2 as the scrambling ID whensignaling UEs that are operating without CE or with small CE (e.g., CElevel of 0 dB) and the BS may use 3 as the scrambling ID when signalingUEs that are operating with a larger CE (e.g., CE level of 10 dB).

A scrambling sequence initialization may be cell-specific, according toaspects of the present disclosure. That is, a BS may use a scramblingsequence initialization for scrambling all MPDCCHs to UEs in a cell,while other BSs may use other scrambling sequence initializations forscrambling MPDCCHs to UEs served in other cells.

According to aspects of the present disclosure, the scrambling sequencemay comprise a demodulation reference signal (DM-RS).

According to aspects of the present disclosure, a BS may transmit ascrambled signal to an enhanced machine type communications (eMTC) UEmultiplexed with a scrambled signal to a non-eMTC UE in a same resourceblock.

According to aspects of the present disclosure, a UE may receive ascrambled signal from a BS, initialize a scrambling sequence based on aCE level of the UE, and descramble the scrambled signal with thescrambling sequence (e.g., as in operation 1200 in FIG. 12 above). Thescrambled sequence may comprise a DM-RS. Another signal may bemultiplexed with the scrambled signal in a same resource block.

According to aspects of the present disclosure, a UE may monitor MPDCCHof different repetition levels for the reception of a paging channel.For example, the eNB may transmit MPDCCHs related to paging withrepetition levels R selected from the set {1, 4, 32, 256}. The largevariability in numbers of repetition of MPDCCHs allows an eNB toaccommodate UEs with widely varying coverage levels. In some cases, a UEin good coverage may need to monitor only the lower repetition levels(e.g., Rϵ{1, 4}), and if the eNB transmits with a larger repetitionlevel the UE may early decode. For example, if eNB transmits with R=32,the UE may be able to early decode with a lower number of repetitions(e.g., R=8). That is, while the eNB transmits the MPDCCH 32 times(repetition level 32) in the example, the UE may correctly decode theMPDCCH after the eighth repetition, and the UE may deactivate a receiverafter the eighth repetition, thus conserving power. It may be importantfor a UE to correctly assess the repetition levels to monitor to reducepower consumption of the UE while keeping good reliability incommunications.

According to aspects of the present disclosure, a BS (e.g., the BSmentioned in FIG. 7 and/or FIG. 15) may determine a set of repetitionsfor transmitting a downlink channel, based at least in part on acoverage enhancement (CE) level of a UE, determine a power boost valuefor the downlink channel, transmit an indication of the power boostvalue for the downlink channel, and transmit the downlink channel basedon the set of repetitions and the power boost value. The BS maydetermine different power boost values for at least one repetition inthe set of repetitions. That is, a BS may determine how much to powerboost a channel to a UE and how many repetitions to use based oninformation of the CE level of the UE, and then the BS may transmit thechannel (e.g., an MPDCCH) to the UE for the determined number ofrepetitions, with each repetition power boosted one of the determinedamounts.

In some cases, assessment of the repetition levels to monitor by a UEmay be made based on measured received signal quality. For example, a UEmay measure downlink RSRP, RSRQ, and/or signal to noise ratio (SNR)based on a cell-specific reference signal, and the UE may decide therepetition level to monitor for paging based at least in part on thismeasurement. According to aspects of the present disclosure, a UE maydetermine a necessary repetition level to decode MPDCCHs up to a certainreliability (e.g., a 1% missed detection rate) and select to monitor alowest repetition level from a set of repetition levels that meets thatrequirement. For example, a UE may have a reliability requirement toreceive MPDCCHs with a rate of missed detections of 1%, determine thatrepetition levels of 32 and 256 both meet that requirement, and selectto monitor for MPDCCHs at a repetition level of 32 because it is lowerthan the repetition level of 256.

In some cases, MPDCCHs for paging may be power boosted to reducedecoding time for a UE in deep coverage. When MPDCCHs for paging arepower boosted, the UE may take into account a power boost value ofMPDCCHs when assessing a repetition level or levels to monitor. The UEmay determine a necessary repetition level to decode MPDCCHs up to acertain reliability (e.g., 1% miss detection rate) and pick the lowestrepetition level that meets that requirement while taking into accountthe power boost value of the MPDCCHs. For example, if a UE determines aSNR value for signals from an eNB is −5 dB, and the power boost valuefor MPDCCHs for paging is 3 dB, then the UE may determine to monitorMPDCCHs using a repetition level based on an effective SNR value of−5+3=−2 dB. The power boost value used by an eNB may be broadcast by theeNB in system information, communicated to a UE in a unicast manner(e.g. by RRC message), or conveyed by higher layer signaling.Furthermore, different repetition levels may have different power boostvalues, so the eNB may determine and transmit indications of a set ofpower boost values corresponding to each (or a subset) of the repetitionlevels, and a UE may determine a subset of the repetition levels or amaximum repetition level based at least in part on a measured receivedsignal quality and the indicated set of power boost values. As above,the eNB may broadcast the indications of the set of power boost values,transmit the indications in a unicast manner, or convey the indicationsby higher layer signaling.

According to aspects of the present disclosure, a UE (e.g., the UEmentioned in FIG. 8) may receive a paging signal in a second searchspace in a third narrowband region. That is, a UE may transmit a PRACHsignal on a first narrowband region, receive a RAR message responding tothe PRACH on a second narrowband region, and receive a paging signal inanother search space in third narrowband region.

According to aspects of the present disclosure, a UE (e.g., the UEmentioned in FIG. 8 and/or FIG. 15) may determine a first set ofrepetitions for receiving a downlink channel, based at least in part ona maximum coverage enhancement (CE) level supported by the BS, determinea received signal quality, determine a second set of repetitions forreceiving the downlink channel based at least in part on the first setof repetitions and the received signal quality, and receive the downlinkchannel based on the second set of repetitions. The UE may furtherreceive an indication of a power boost value for the downlink channeland determine the second set of repetitions for receiving the downlinkchannel further based on the indication of the power boost value. Theindication of the power boost value for the downlink channel mayindicate different power boost values for different repetitions in thefirst set of repetitions. Additionally or alternatively, the downlinkchannel may be a control channel associated with a paging channel. Alsoadditionally or alternatively, the UE may move to a discontinuousreception (DRX) mode if the UE does not receive the downlink channel.

FIG. 15 illustrates an exemplary transmission timeline 1502 of a BS(e.g., eNB 110 a shown in FIG. 1) and an exemplary transmission timeline1510 of a UE (e.g., UE 120 a shown in FIG. 1) operating according toaspects of the present disclosure. The UE may be an MTC UE, aspreviously described. In the exemplary timelines 1502 and 1510, eachblock represents one subframe. During the time 1504, the BS transmits anMPDCCH at a repetition level of 32. The MPDCCH may be, for example,scheduling a PDSCH directed to an MTC UE, such as UE 120 a shown inFIG. 1. The MPDCCH may be power boosted, as described previously above.In the example timelines, the MPDCCH is power boosted, and the MTC UEreceives and successfully decodes the MPDCCH in eight subframes duringthe time shown at 1512. The MTC UE has information regarding therepetition level used by the BS, and powers off a receiver of the MTC UEfor the remaining portion of the time 1514, as illustrated by theunfilled boxes. During the time 1506, the BS transmits the PDSCHscheduled by the MPDCCH to the MTC UE. During the time 1516, the UEactivates the receiver of the UE and receives and decodes the PDSCH. Asillustrated, the MTC UE may keep the receiver active for the 32subframes of the repetition level, if needed, to successfully receivethe PDSCH.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover a, b, c,a-b, a-c, b-c, and a-b-c, as well as any combination with multiples ofthe same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b,b-b-b, b-b-c, c-c, and c-c-c or any other ordering of a, b, and c).

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Examplesof processors include microprocessors, microcontrollers, digital signalprocessors (DSPs), field programmable gate arrays (FPGAs), programmablelogic devices (PLDs), state machines, gated logic, discrete hardwarecircuits, and other suitable hardware configured to perform the variousfunctionality described throughout this disclosure. Software shall beconstrued broadly to mean instructions, instruction sets, code, codesegments, program code, programs, subprograms, software modules,applications, software applications, software packages, routines,subroutines, objects, executables, threads of execution, procedures,functions, etc., whether referred to as software, firmware, middleware,microcode, hardware description language, or otherwise. A softwaremodule may reside in RAM memory, flash memory, ROM memory, EPROM memory,EEPROM memory, PCM (phase change memory), registers, hard disk, aremovable disk, a CD-ROM or any other form of storage medium known inthe art. An exemplary storage medium is coupled to the processor suchthat the processor can read information from, and/or write informationto, the storage medium. In the alternative, the storage medium may beintegral to the processor. The processor and the storage medium mayreside in an ASIC. The ASIC may reside in a user terminal. In thealternative, the processor and the storage medium may reside as discretecomponents in a user terminal. Generally, where there are operationsillustrated in Figures, those operations may have correspondingcounterpart means-plus-function components with similar numbering.

In one or more exemplary designs, the functions described may beimplemented in hardware, software or combinations thereof. Ifimplemented in software, the functions may be stored on or transmittedover as one or more instructions or code on a computer-readable medium.Computer-readable media includes both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage media may be anyavailable media that can be accessed by a general purpose or specialpurpose computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code means in the form of instructions or data structures andthat can be accessed by a general-purpose or special-purpose computer,or a general-purpose or special-purpose processor. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared, radio,and microwave, then the coaxial cable, fiber optic cable, twisted pair,DSL, or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and Blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable media.

The previous description of the disclosure is provided to enable anyperson skilled in the art to make or use the disclosure. Variousmodifications to the disclosure will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other variations without departing from the spirit or scopeof the disclosure. Thus, the disclosure is not intended to be limited tothe examples and designs described herein, but is to be accorded thewidest scope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. An apparatus for wireless communications,comprising: a transmitter configured to transmit a physical randomaccess channel (PRACH) signal to a base station (BS) in a firstnarrowband region comprising one to six resource blocks (RBs) within awider uplink (UL) system bandwidth; and a receiver configured toreceive, in response to the PRACH signal, a random access response (RAR)message in a first search space, which is in a second narrowband regioncomprising one to six RBs within a wider downlink (DL) system bandwidth,in at least a first subframe.
 2. The apparatus of claim 1, wherein thereceiver is further configured to: receive a paging signal in a secondsearch space in a third narrowband region comprising one to six RBswithin the wider DL system bandwidth.
 3. The apparatus of claim 2,further comprising at least one processor coupled to memory, the memorycomprising instructions executable by the at least one processor tocause the apparatus to: determine a first set of repetitions forreceiving a downlink channel, based at least in part on a maximumcoverage enhancement (CE) level supported by the BS; determine areceived signal quality; and determine a second set of repetitions forreceiving the downlink channel based at least in part on the first setof repetitions and the received signal quality; wherein the receiver isconfigured to receive the downlink channel based on the second set ofrepetitions.
 4. The apparatus of claim 3, wherein: the receiver isconfigured to receive an indication of a power boost value for thedownlink channel; and the memory further comprising instructionsexecutable by the at least one processor to cause the apparatus todetermine the second set of repetitions for receiving the downlinkchannel further based on the indication of the power boost value.
 5. Theapparatus of claim 4, wherein the indication of the power boost valuefor the downlink channel includes at least one different power boostvalue for at least one repetition in the first set of repetitions. 6.The apparatus of claim 3, wherein the downlink channel is a controlchannel associated with a paging channel.
 7. The apparatus of claim 3,wherein the memory comprising instructions executable by the at leastone processor to cause the apparatus to move to a discontinuousreception mode (DRX) if the downlink channel is not received.
 8. Theapparatus of claim 1, further comprising at least one processor coupledto memory, the memory comprising instructions executable by the at leastone processor to cause the apparatus to identify a third search space ina fourth narrowband region comprising one to six RBs within the wider DLsystem bandwidth for receiving RAR messages based at least in part on acoverage enhancement (CE) level of the UE; wherein the receiver isconfigured to receive information regarding the first search space and afirst CE level for the first search space in a system information block(SIB); and wherein the receiver is configured to receive informationregarding the third search space and a second CE level for the thirdsearch space in at least one of the SIB or another SIB.
 9. The apparatusof claim 1, further comprising at least one processor coupled to memory,the memory comprising instructions executable by the at least oneprocessor to cause the apparatus to determine a RAR response window, aset of machine type communications (MTC) physical downlink controlchannel (MPDCCH) starting point subframes, a RAR offset number ofsubframes, and a bundle size for each of a plurality of coverageenhancement (CE) levels.
 10. The apparatus of claim 1, furthercomprising at least one processor coupled to memory, the memorycomprising instructions executable by the at least one processor tocause the apparatus to determine a radio frequency within the wider DLsystem bandwidth for paging, a time for paging, a bundle size forpaging, and a set of monitoring candidates based at least on a maximumcoverage enhancement (CE) level supported by the BS.
 11. The apparatusof claim 10, wherein the receiver is further configured to receiveinformation regarding the maximum CE level supported by the BS.
 12. Theapparatus of claim 1, wherein the receiver is further configured toreceive at least one of a system information (SI) change or earthquakeand tsunami warning system (ETWS) signal in the second narrowbandregion.
 13. The apparatus of claim 1, wherein the receiver is furtherconfigured to receive at least one system information (SI) change orearthquake and tsunami warning system (ETWS) signal in a broadcastchannel of the wider DL system bandwidth during at least a secondsubframe.
 14. An apparatus for wireless communications, comprising: areceiver configured to: receive a first demodulation reference signal(DM-RS) scrambled with a first scrambling sequence initialized with ascrambling sequence initialization; and receive a signal scrambled withthe first scrambling sequence in a search space, wherein at least asecond DM-RS scrambled with a second scrambling sequence initializedwith the scrambling sequence initialization is transmitted in the searchspace; and at least one processor coupled to memory, the memorycomprising instructions executable by the at least one processor tocause the apparatus to descramble the signal with the first scramblingsequence.
 15. The apparatus of claim 14, wherein the scrambling sequenceinitialization comprises a cell-specific scrambling sequenceinitialization.
 16. An apparatus for wireless communications,comprising: means for transmitting a physical random access channel(PRACH) signal to a base station (BS) in a first narrowband regioncomprising one to six resource blocks (RBs) within a wider uplink (UL)system bandwidth; and means for receiving, in response to the PRACHsignal, a random access response (RAR) message in a first search space,which is in a second narrowband region comprising one to six RBs withina wider downlink (DL) system bandwidth, in at least a first subframe.17. The apparatus of claim 16, further comprising: means for receiving apaging signal in a second search space in a third narrowband regioncomprising one to six RBs within the wider DL system bandwidth.
 18. Theapparatus of claim 17, further comprising: means for determining a firstset of repetitions for receiving a downlink channel, based at least inpart on a maximum coverage enhancement (CE) level supported by the BS;means for determining a received signal quality; means for determining asecond set of repetitions for receiving the downlink channel based atleast in part on the first set of repetitions and the received signalquality; and means for receiving the downlink channel based on thesecond set of repetitions.
 19. The apparatus of claim 18, furthercomprising: means for receiving an indication of a power boost value forthe downlink channel; and means for determining the second set ofrepetitions for receiving the downlink channel further based on theindication of the power boost value.
 20. The apparatus of claim 19,wherein the indication of the power boost value for the downlink channelincludes at least one different power boost value for at least onerepetition in the first set of repetitions.
 21. The apparatus of claim18, wherein the downlink channel is a control channel associated with apaging channel.
 22. The apparatus of claim 18, further comprising meansfor moving to a discontinuous reception mode (DRX) if the downlinkchannel is not received.
 23. The apparatus of claim 16, furthercomprising: means for identifying a third search space in a fourthnarrowband region comprising one to six RBs within the wider DL systembandwidth for receiving RAR messages based at least in part on acoverage enhancement (CE) level of the UE; means for receivinginformation regarding the first search space and a first CE level forthe first search space in a system information block (SIB); and meansfor receiving information regarding the third search space and a secondCE level for the third search space in at least one of the SIB oranother SIB.
 24. The apparatus of claim 16, further comprising: meansfor determining a RAR response window, a set of machine typecommunications (MTC) physical downlink control channel (MPDCCH) startingpoint subframes, a RAR offset number of subframes, and a bundle size foreach of a plurality of coverage enhancement (CE) levels.
 25. Theapparatus of claim 16, further comprising: means for determining a radiofrequency within the wider DL system bandwidth for paging, a time forpaging, a bundle size for paging, and a set of monitoring candidatesbased at least on a maximum coverage enhancement (CE) level supported bythe BS.
 26. The apparatus of claim 25, further comprising: means forreceiving information regarding the maximum CE level supported by theBS.
 27. The apparatus of claim 16, further comprising: means forreceiving at least one of a system information (SI) change or earthquakeand tsunami warning system (ETWS) signal in the second narrowbandregion.
 28. The apparatus of claim 16, further comprising: means forreceiving at least one system information (SI) change or earthquake andtsunami warning system (ETWS) signal in a broadcast channel of the widerDL system bandwidth during at least a second subframe.
 29. An apparatusfor wireless communications, comprising: means for receiving a firstdemodulation reference signal (DM-RS) scrambled with a first scramblingsequence initialized with a scrambling sequence initialization; meansfor receiving a signal scrambled with the first scrambling sequence in asearch space, wherein at least a second DM-RS scrambled with a secondscrambling sequence initialized with the scrambling sequenceinitialization is transmitted in the search space; and means fordescrambling the signal with the first scrambling sequence.
 30. Theapparatus of claim 29, wherein the scrambling sequence initializationcomprises a cell-specific scrambling sequence initialization.
 31. Anon-transitory computer readable medium for wireless communications byan apparatus, the computer readable medium including instructions that,when executed by a processing system, cause the apparatus to performoperations comprising: transmitting a physical random access channel(PRACH) signal to a base station (BS) in a first narrowband regioncomprising one to six resource blocks (RBs) within a wider uplink (UL)system bandwidth; and receiving, in response to the PRACH signal, arandom access response (RAR) message in a first search space, which isin a second narrowband region comprising one to six RBs within a widerdownlink (DL) system bandwidth, in at least a first subframe.
 32. Thenon-transitory computer readable medium of claim 31, wherein theoperations further comprise: receiving a paging signal in a secondsearch space in a third narrowband region comprising one to six RBswithin the wider DL system bandwidth.
 33. The non-transitory computerreadable medium of claim 32, wherein the operations further comprise:determining a first set of repetitions for receiving a downlink channel,based at least in part on a maximum coverage enhancement (CE) levelsupported by the BS; determining a received signal quality; determininga second set of repetitions for receiving the downlink channel based atleast in part on the first set of repetitions and the received signalquality; and receiving the downlink channel based on the second set ofrepetitions.
 34. The non-transitory computer readable medium of claim33, wherein the operations further comprise: receiving an indication ofa power boost value for the downlink channel; and determining the secondset of repetitions for receiving the downlink channel further based onthe indication of the power boost value.
 35. The non-transitory computerreadable medium of claim 34, wherein the indication of the power boostvalue for the downlink channel includes at least one different powerboost value for at least one repetition in the first set of repetitions.36. The non-transitory computer readable medium of claim 33, wherein thedownlink channel is a control channel associated with a paging channel.37. The non-transitory computer readable medium of claim 33, wherein theoperations further comprise moving to a discontinuous reception mode(DRX) if the downlink channel is not received.
 38. The non-transitorycomputer readable medium of claim 31, wherein the operations furthercomprise: identifying a third search space in a fourth narrowband regioncomprising one to six RBs within the wider DL system bandwidth forreceiving RAR messages based at least in part on a coverage enhancement(CE) level of the UE; receiving information regarding the first searchspace and a first CE level for the first search space in a systeminformation block (SIB); and receiving information regarding the thirdsearch space and a second CE level for the third search space in atleast one of the SIB or another SIB.
 39. The non-transitory computerreadable medium of claim 31, wherein the operations further comprise:determining a RAR response window, a set of machine type communications(MTC) physical downlink control channel (MPDCCH) starting pointsubframes, a RAR offset number of subframes, and a bundle size for eachof a plurality of coverage enhancement (CE) levels.
 40. Thenon-transitory computer readable medium of claim 31, wherein theoperations further comprise: determining a radio frequency within thewider DL system bandwidth for paging, a time for paging, a bundle sizefor paging, and a set of monitoring candidates based at least on amaximum coverage enhancement (CE) level supported by the BS.
 41. Thenon-transitory computer readable medium of claim 40, wherein theoperations further comprise: receiving information regarding the maximumCE level supported by the BS.
 42. The non-transitory computer readablemedium of claim 31, wherein the operations further comprise: receivingat least one of a system information (SI) change or earthquake andtsunami warning system (ETWS) signal in the second narrowband region.43. The non-transitory computer readable medium of claim 31, wherein theoperations further comprise: receiving at least one system information(SI) change or earthquake and tsunami warning system (ETWS) signal in abroadcast channel of the wider DL system bandwidth during at least asecond subframe.
 44. A non-transitory computer readable medium forwireless communications by an apparatus, the computer readable mediumincluding instructions that, when executed by a processing system, causethe apparatus to perform operations comprising: receiving a firstdemodulation reference signal (DM-RS) scrambled with a first scramblingsequence initialized with a scrambling sequence initialization;receiving a signal scrambled with the first scrambling sequence in asearch space, wherein at least a second DM-RS scrambled with a secondscrambling sequence initialized with the scrambling sequenceinitialization is transmitted in the search space; and descrambling thesignal with the first scrambling sequence.
 45. The non-transitorycomputer readable medium of claim 44, wherein the scrambling sequenceinitialization comprises a cell-specific scrambling sequenceinitialization.